Parsing xml file with animation nodes
The ElementTree.parse() function takes a filename or file object for the xml file as an argument. In your script node, xml is a string and not a filename or a file object and hence the error.

Instead, you can use the ElementTree.fromstring() function which takes a string representing the xml file. Note that the output is the root of the tree and thus getroot() needn't be used.

See the documentation.